I thought I would put this out there while I remembered… I’ve been having the p420 come up and I clear it and it comes back shortly under no particular condition. I will be thoroughly cleaning the intake manifold as suggested by others now that I am tearing down for a head gasket replacement on my ‘95. However, during the removal of the exhaust manifolds I noticed that the rear two hard-to-get-to fasteners were little more than hand tight. Nice for removal purposes, but not so great for getting a good seal at the EGR port. I’ll still do the intake manifold scouring, but I’d be surprised if this was not the issue. I’ll post back on reassembly whether it is solved. But in the meantime, an easy check for anyone having this issue!
